Rupture of 6056 aluminum sheet materials: Effect of sheet thickness on strain localization and toughness

摘要

This study deals with the role of sheet thickness on ductility tearing resistance of a 6056 aluminum alloy. Tensile tests on smooth and U or V-notched flat samples and tests on Kahn specimens were conducted. Microstructural analysis shows that damage initiates at intermetallic precipitates and that final rupture is caused by shearing of the matrix ligaments between the broken precipitates. The apparent macroscopic ductility increases with thickness. This effect is highest for smooth and moderately notched samples. The opposite trend was observed for V-notched and Kahn samples. The analysis of the experiments is based on finite element simulations of the tests. The material behavior is described by the Rousselier damage model modified to account for both plastic anisotropy and damage nucleation at precipitates. Simulations are post-processed to evaluate the Rice condition for localization. On one hand, failure of moderately notched specimens is essentially controlled by plastic instability and damage plays a limited role. On the other hand, failure of Kahn specimens is controlled by damage growth. The stability analysis corroborates well with experiments showing the increased resistance of thick specimens.